anecdotal evidence is what you are asking for. Like asking how many people you know personally who got electrocuted. After all, it doesn't really happen very often now, does it? Sewer gases can be undetected by the human nose, and can kill you. If you ask how many people really have died from sewer gases, you would find it happens every year.

If its a top quality rubber, or composite with a good SS spring, I'll bet they last the life of the fixture or room until the next remodel. Approved use of them would save millions in roof holes and materials wasted.

I've experienced a bad AAV before, that bathroom smelled pretty bad.
So yes, like "any" mechanical device, it does happen.
You know the rubber flappers in toilets? Those get replaced.

When a homeowner has a smelly bathroom or kitchen, do they have enough knowledge to trouble shoot the problem? No. Not really, so when these problems do occur, they aren't reported or repaired.
The reason plumbers like a "real" vent in the wall and up through the roof, is that they don't need to be "fixed". They are pretty much install and forget.
Not that AAV's don't have their place, but for the same money in parts, and an insignificant amount of installation time, it makes way more sense to run a solid vent.

AAVs are no substitute for a proper open vent. And don't forget, sometimes the best way to snake a line is through the roof vent...having AAVs everywhere would eliminate that option, and require ugly access panels everywhere!

If its a top quality rubber, or composite with a good SS spring, I'll bet they last the life of the fixture or room until the next remodel. Approved use of them would save millions in roof holes and materials wasted.

Nope...can't say I have seen a bad one. The problem that worries me is , they are often installed below the flood rim, so on occasion if there is a bad backup, that rubber seal area is vulnerable to being fouled. Who know what happens the next time?

I would say they have become a fact of life, and just one more thing to deal with.